Flat panel display and a method of fabrication therefor

ABSTRACT

Provided herein is a method for fabricating an array. A plurality of insulating media are formed having a plurality of wavelength and polarizing elements embedded therein at an angle relative to the surfaces of the media, such that the spacing between elements halves for each different medium. A phase shifter arrangement is also formed such that a portion of conductive material is disposed on a surface of the insulating media in registry with every other element in each of the media, and other portions of conductive material disposed on another surface overlapping said elements. A phase shifting material is disposed over at least said every other element. The media are stacked such that the topmost insulating medium has two elements, and each succeeding medium has twice as many elements as a preceding medium.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to display devices forbeam steering and scanning and, more particularly, to flat panel displaydevices for beam steering and scanning which are electronic in characterand which further incorporate logic trees which are designed to steerelectromagnetic energy so that both transmission losses and the numberof energizing sources of an imaging array are minimized. The devicesinclude a multi-stage imaging array made up of a plurality of stackedlogic trees so arranged that each stage of each logic tree includesactive steering elements which access twice as many like steeringelements and associated passive steering elements in each succeedingstage. The active and passive elements incorporate cholesteric liquidcrystal (CLC) elements which are polarization sensitive disposed withinthem at an angle of 45°. The active elements include variable half-waveretarders which, under control of a programmable pulsed source changethe polarization of incident energy on CLC elements and provide ascanned line of electromagnetic energy to the imaging cells disposed atthe output of each logic tree. In such an arrangement, arraytransmission losses are minimized and one source of electromagneticenergy per logic tree is required.

[0003] In another arrangement using a similar imaging array,transmission losses are reduced over prior art input arrangements andthe number of sources of electromagnetic energy is reduced to one. Usingan input logic tree, fed from a single laser and arrangedperpendicularly to the array logic trees, the imaging cells of the inputlogic tree act as inputs to the stacked logic trees of the imagingarray. In this way, a scanned line is delivered from each imaging cellof the input logic tree to the first active element of an associatedarray logic tree. From there, under control of a programmable pulsedgenerator, portions of the scanned line are directed to the outputimaging cells of each of the array logic trees. Two-dimensional imagesare built up in this way by activating the imaging cells of each arraylogic tree in succession. Three dimensional images may be obtained usingan approach similar to that just described by interleaving stereodisplaced images from a 3-D camera at the output imaging cells of animaging array by activating the first and every other logic tree of anarray with one image and the second and every other logic tree with astereo displaced image. Glasses which respond to a differentpolarization for each eye are required to produce the 3-D effect.

[0004] The present invention also relates to a method of fabricating theabove described imaging arrays by slicing stacked alternating layers ofinsulating material and CLC material. To the extent that a final imagingarray requires that each logic tree have twice as many CLC elements perstage as a preceding stage after the first stage, the number of CLCelement per stage may doubled by halving the spacing between CLCelements during fabrication. This is accomplished by halving thethickness of the insulation disposed between layers of CLC materialafter setting the initial spacing between CLC layers which are to beused as the first stage of a logic tree. After producing layers of agiven thickness by slicing at a 45° angle, transparent metallic groundplanes are formed. Then, using photolithographic and etching techniques,electrodes are formed over every other CLC element. A spacer element isthen fixed to the periphery of each layer and the resulting volume isfilled with a phase shifter material. The resulting stages are thenstacked using as many as required to form an imaging array with adesired number of imaging cells. Stacking the stages, which are slicescontaining differently spaced CLC elements automatically provides thelogic trees which deliver scanned line to the output imaging cells. Themethod uses mass-production techniques and results in an inexpensive,flat-panel display.

[0005] 2. Description of the Prior Art

[0006] Generally, there are two well-known techniques for the steeringand scanning of light beams. One is electromechanical and the other isacousto-optical. Both techniques have severe limitations. One suchlimitation is that arrangements incorporating these techniques require alarge volume due to the small angel through which the light beam can bedeflected. Thus, if it is desired to scan a length B, the deflectionarrangement has to be positioned a distance, A, providing an A/B rationlarger than 1.

[0007] All known systems require an A/B ratio larger than 1 and to theextent that the arrangement of the present application can provide A/Bratios which are very much less than 1, the resulting structure may alsobe characterized as a flat-panel display. In the known scanningapproaches, scanning speed is relatively sluggish due to the use ofelectromechanical or electro-acoustic elements. Because such devices areeliminated in the scanning arrangement of the present application,scanning speeds in the microsecond range are achievable.

[0008] U.S. Pat. No. 4,670,744 filed Mar. 14, 1985 and issued Jun. 2,1987 in the name of T. Buzak incorporates variable optical retarders andliquid crystal chiral cells. This reference takes advantage of thereflective and transmissive characteristics of chiral cells as well asthe ability of variable optical retarders to convert one circularpolarization to the other circular polarization. However, when a beamcontaining image information is projected along a given path in whichthe chiral cells and retarders are disposed, the beam remains in thatgiven path or is retroreflected along the same path. Opposed to this,the arrangements of the present application while they all incorporatethe reflection-transmission characteristics of chiral cells, they allincorporate an ability to divert the reflected beams into other paths.To the extent that the Buzak reference seek to provide athree-dimensional display, all the images reflected must lie in a planeparallel to the planes of the chiral cells. Otherwise distortion anddegradation of the reflected images would occur due to the requiredlateral displacement of the chiral cells. In other words, to provide thedesired result, no diversion of the beam in the Buzak reference can betolerated.

[0009] U.S. Pat. No. 5,221,982, filed Jul. 5, 1991 and issued on Jun.22, 1993 to S. M. Faris is entitled Polarizing Wavelength Separator. Thepatent relates to a polarizing wavelength separating optical element inthe form of a flat panel which causes each of a plurality ofpolychromatic optical beams from a source, entering at one surface andtransmitted to another surface, to be converted, with high conversionefficiency, into circularly polarized, spectrally and spatiallyseparated beams. The element is made of a periodic array of cells; eachof the latter incorporating a plurality of subcells. One subcellfunctions as a broadband reflector, while each of the remaining subcellsacts as a polarizing, wavelength selective reflector. Each subcellcomprises a plurality of layers which are bonded together at theirsurfaces and are oriented at a 45° angle relative to the horizontalsurfaces of the panel. In each subcell, the plurality of layers comprisetwo cholesteric liquid crystal, CLC films, which reflect at a selectedwavelength, at least one optical retarder and clear substrates whichprovide mechanical support. The thicknesses of the supporting substratesare designed to cause the beams transmitted through the element to bespatially separated by appropriate distances.

[0010] In the reference, all the elements utilized in the panel arepassive in character which constrain beams of electromagnetic energyinto paths which are fixed for all time. In contradistinction to this,the present application, with it electronically controllable retarders,provides paths for electromagnetic energy which can be changed frominstant-to-instant taking advantage of both the transmissive andreflective capabilities of CLC elements. The combination of a circularlypolarized input with controllable retarders and associated CLC elementsin the present invention provides the ability to scan a beam from pointto point in a panel-like display or to steer a beam it can emanate fromany location on an array of imaging cells. Strictly passive arrays withtheir fixed paths cannot achieve these results.

[0011] U.S. Pat. No. 5,459,591, filed Mar. 9, 1994 and issued Oct. 17,1995 to S. M. Faris relates to beam steering and scanning devices whichutilize an imaging cell which incorporates a solid-state cholestericliquid crystal (CLC) element, an electronically controlled, variablehalf-wave retarder and a source of circularly polarized light. The CLCelement is disposed to an angle (45°) relative to the path along whichlight from the source is projected and is designed to reflect, at agiven wavelength, one circular polarization of light and transmit theother. Using this characteristic, light of one polarization or the otheris presented to the variable retarder and depending on whether or not itis actuated, light is either diverted into another orthogonal path orremains in the original path. If another similar imaging cell isdisposed in the orthogonal path, light incident on that cell can also bediverted into yet another path or transmitted along the orthogonal pathunder control of a half-wave retarders associated with said anotherimaging cells. By arranging a plurality of imaging cells in the form ofan array and accessing each row of the cells of the array with a columnof similar imaging cells and by selectively activating half-waveretarders associated with each of the cells, monochromatic orpolychromatic light from a single source or multiple sources may besteered to a selected cell and reflected from its associated CLC elementor elements. Utilizing successive cells in the array and causingreflection of a modulated beam or beams provides a frame in the mannerof the usual TV set which is viewed by the eyes as an integratedpicture. Successive frames, of course, provide the usual moving images.

SUMMARY OF THE INVENTION

[0012] The present invention relates to beam steering and scanningdevices which utilize cholesteric liquid crystal (CLC) elements arrangedin branches to form a logic tree. Each branch comprises an active andpassive CLC element; the former further comprising a half-wave retarderand an electrode and the latter only the CLC element. Each succeedingbranch contains twice as many branches as a preceding branch and, byactivating active CLC element electrodes under control of a programmablepulsed source, inputs applied to the first stage of a logic tree aredelivered as a scanned line of electromagnetic energy or light to theimaging cells of the last stage of the logic tree. By stacking identicallogic trees with a laser source for each tree, a flat panel imagingarray or display device is formed in which the transmission losses areminimized.

[0013] Using a similar imaging array, transmission losses may be furtherreduced by using a logic tree the outputs of which act as inputs to theimaging array where formerly a plurality of lasers were required. Bypositioning an input logic tree perpendicularly to the similar logictrees of the imaging array, a single source of energy provides an outputat each of its imaging cells which acts as an input to an associatedlogic tree of the imaging array. 2-D and 3-D images are provided byapplying modulation to lasers from standard T.V. cameras and camerasdesigned to provide stereo displaced images respectively. In the arraywhich provides 3-D images, an image and a stereo displaced image areinterleaved to provide the desired images each of which has a differentcircular polarization.

[0014] The present invention also relates to a method of fabricatingstructures which provide the above described features. Since all thestages of a logic tree differ only in the number of branches theycontain, it was recognized that light beams, for example, applied from alaser beam could pass through a number of stages with minimum dispersionand maintain its original position even though relatively largestructures are used to control its position. This recognition permittedthe use of CLC elements, electrodes and half-wave retarder materialwhich need not be divided into discrete elements in each logic tree.Thus, each CLC element, each electrode and each retarder material mayextend from top-to-bottom or from side-to-side in each stage of animaging array.

[0015] Stages are fabricated by slicing layers of insulating materialand CLC material at an angle of 45°. The thickness of the insulatingmaterial controls the spacing between the resulting CLC elements.Transparent layers, such as indium tin oxide are formed on both sides ofthe layer or layers containing spaced CLC elements. Usingphotolithographic techniques, one side is masked and etched to form anelectrode over every other CLC element. A spacer element fixed to theperiphery of each layer where the electrodes have been etched forms avolume into which half-wave retarder material is introduced in liquidform. In this way, stages containing two, four, eight, sixteen, CLCelements and so on have been massed produced. The stages are thenstacked so that each stage contains twice as many CLC elements as apreceding stage forming logic trees the imaging cells of which form anarray.

[0016] The above described arrangements and their fabrication techniqueprovide flat panel displays which substantially reduce transmissionlosses and the number of energizing sources. These features combinedwith a novel and inexpensive manufacturing technique are able to delivera flat panel display which requires neither a vacuum envelope norunacceptable high voltages.

[0017] It is, therefore, an object of the present invention to providean imaging array which has reduced transmission losses compared to priorart arrays.

[0018] Another object is to provide an imaging array which reducestransmission losses while simultaneously reducing the electromagneticsource requirement to one source.

[0019] Still another object is to provide an improved flat panel displaywhich is capable of providing both 2-D and 3-D images.

[0020] Still another object is to provide a method of fabricating flatpanel display which is inexpensive and conducive to mass-productiontechniques.

[0021] The foregoing objects and features of the present invention willbecome apparent from the following more detailed description ofpreferred embodiments taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a schematic drawing of a logic tree of active andpassive Cholesteric Liquid Crystal (CLC) elements so arranged that asingle input to a first stage of the logic tree may be delivered to anyone of the outputs of the last stage of the logic tree.

[0023]FIG. 2 is a schematic diagram of a logic tree similar to thatshown in FIG. 1 which shows that the polarization of CLC members may bevaried to produce outputs having polarizations different from thoseshown in FIG. 1.

[0024]FIG. 3 is an orthographic projection of eight logic treespositioned one atop the other which, in accordance with the presentinvention, provide 64 outputs using one source of electromagneticradiation per logic tree.

[0025]FIG. 4 is an orthographic projection similar to FIG. 3 exceptthat, instead of a plurality of sources of electromagnetic radiation,only a single source of radiation in combination with a logic tree likethat shown in FIG. 1 and disposed perpendicularly to the stacked logictrees of FIG. 3 is required.

[0026]FIG. 5 is an orthographic projection of an imaging array and itsassociated electronics which, in conjunction with viewing glasses andstereo displaced images, provides a 3-D display.

[0027]FIG. 6 is an orthographic, cut-away projection of a plurality oflayers of insulating material like SiO₂ and a plurality of layers of CLCmaterial interleaved with the layers of insulating material. Theinterleaved layers are sliced at an angle of 45°.

[0028]FIG. 7 is a cross-sectional view of a layer of insulating materialin which CLC members are disposed at an angle of 45° and are spacedapart by a distance t.

[0029]FIG. 8 is a cross-sectional view of a layer of insulating materialin which CLC members are disposed at an angle of 45° and is similar toFIG. 7 except that the CLC members are spaced apart by a distance t/2.

[0030]FIG. 9 is a cross-sectional view similar to that shown in FIG. 7except that the CLC members are spaced apart by a distance t/4.

[0031]FIG. 10 is a cross-sectional, orthographic projection of aninsulation layer with CLC members disposed at an angle of 45° thereinlike that shown in FIG. 8 and further includes a ground plane disposedon the bottom thereof.

[0032]FIG. 11 is a cross-sectional orthographic projection similar toFIG. 10 except that it further includes electrodes disposed over everyother CLC member.

[0033]FIG. 12 is a cross-sectional view similar to that shown in FIG. 11further including a spacer disposed around the periphery of the layer ofinsulation material with the resulting enclosed volume filled with aphase-shifter material in liquid form.

[0034]FIG. 13 is a top view of a logic tree made up of layers like thoseshown in FIGS. 7-12 after they have been stacked and aligned to form anarray like those shown in FIGS. 4, 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0035] Referring now to FIG. 1, there is shown a schematic drawing of alogic tree of active and passive Cholesteric Liquid Crystal (CLC)elements which are so arranged and controlled that a single input to afirst stage of the logic tree may be delivered to any one of the outputsof the last stage of the logic tree by appropriately switchingelectronically controlled half-wave retarders associated with the activeCLC elements of the logic tree. By programming the switching of thehalf-wave retarders of each stage of the logic tree, a laser input tothe first stage of the logic tree may, for example, provide a scannedversion of the input at the outputs of the last stage of the logic tree.The application of the logic tree as a scanner will be described indetail in what follows. It will also become clear that the sameembodiment has other applications.

[0036] Considering FIG. 1 in more detail, logic tree 1 is shownconsisting of a plurality of stages labeled STAGE 1-STAGE 4 wherein eachstage includes one or more branches each of which consists of an activeand passive CLC element. Thus, STAGE 1 consists of a branch 2 which, inturn, includes active CLC element 18 and passive CLC element 19. STAGE 2consists of branches 3, 4; the former including active CLC element 21and passive CLC element 22 while the latter includes active CLC element23 and passive CLC element 24. STAGE 3 consists of four branches 5-8each of the branches consisting of active and passive CLC elements 31,33, 35, 37 and 32, 34, 36, 38, respectively. Similarly, STAGE 4 consistsof eight branches 9-16 each of these branches including active andpassive CLC elements 41, 43, 45, 47, 49, 51, 53, 55 and 42, 44, 46, 48,50, 52, 54, and 56, respectively, just like the previously mentionedbranches. At this point, it should be appreciated that many more stagesmay be added to tree 1 with each succeeding stages having twice as manybranches as the preceding stage. Using this approach, STAGE 4 in FIG. 1has 2^(n−1) branches wherein n is the stage number. Thus, STAGE 4 has2⁴⁻¹ or eight branches. Since each branch has two CLC elements, eachstage has 2^(n) elements and, for STAGE 4, sixteen elements. Thus, STAGE10, for example, would have 2¹⁰ or 1024 CLC elements providing one lightoutput per element or 1024 outputs.

[0037] Since FIG. 1 is representative of the way logic tree 1 operatesregardless of the number of stages, only four stages have beenincorporated to clearly demonstrate how such a logic tree may be used toprovide a scanned light output from a plurality of elements which areactivated by an input from a single source of electromagnetic energy.

[0038] Before describing the operation of FIG. 1, it should beunderstood that the active CLC elements of each branch in FIG. 1 do notdepart from similar active elements shown in FIG. 1 of U.S. Pat. No.5,459,591 entitled “Electromagnetic Energy Beam Steering Devices” in thename of S. M. Faris, which is hereby incorporated by reference. Thepassive CLC elements of the present invention differ from the active CLCelements in that the passive CLC elements do not incorporate anelectronically controlled, variable half-wave retarder or π-cell. Thus,each branch of logic tree 1 as represented by branch 2 of FIG. 1includes an active CLC element 18 and a passive CLC element 19. Theformer includes a cholesteric liquid crystal member 60, a transparentelectrode 62, a ground plane (not shown), and a controllable half-waveretarder 61 while the latter includes a cholesteric liquid crystalmember which is identical to member 60. Since each of the branches 3, 4,5-8 and 9-16 is identical with branch 2 of FIG. 1, each cholestericliquid crystal element and each half-wave retarder of each branch isidentified with the same reference numbers 60, 61 respectively.

[0039] In FIG. 1, active CLC element 18 and passive CLC element 19 ofbranch 2 both include cholesteric liquid crystal members 60 which aredisposed at an angle, preferably 45°, within each of the elements 18,19. Members 60 are made from a nematic liquid crystal material withchiral additives or polysiloxane side-chain polymers which cause thecigar-shaped molecules to be spontaneously aligned in an opticallyactive structure of either a left-handed or right-handed helix with ahelical pitch, P. The twisting direction and the pitch, P, of thehelices are determined by the nature and concentration of the additives.A CLC member, like member 60, has all its helices aligned in onedirection and is capable of reflecting light, for example, having onecircular polarization having a characteristic wavelength or band ofwavelengths. Cholesteric Liquid Crystal (CLC) members 60 which are usedin the practice of the present invention and their method of fabricationare shown in U.S. Pat. No. 5,221,982, filed Jul. 5, 1991 and issued onJun. 22, 1993 in the name of S. M. Faris. This patent is herewithincorporated by reference. While CLC members 60 are shown in FIG. 1 asbeing single elements, it should be understood that a plurality of CLCmembers 60 may be substituted for each of the members 60 to provide forthe reflection and transmission of circularly polarized radiation havinga plurality of wavelengths or band of wavelengths which are provided bya plurality of sources of electromagnetic radiation. It should beappreciated that, in the practice of the present invention, members 60may be made of any material which can be switched to reflect and/ortransmit electromagnetic energy by the application of electric ormagnetic fields to that material.

[0040] Half-wave retarders or π-cells 61 shown schematically in FIG. 1are of the type shown and described in U.S. Pat. No. 4,670,744, filedMarch 14, 1985 and issued on Jun. 2, 1987 in the name of T. S. Buzak andmay be utilized in the practice of the present invention. The Buzakpatent is herewith incorporated by reference. Alternatively, instead ofCLC films, polarizing reflectors, polarizing prisms or McNeill prismsmay be utilized in the practice of the present invention and arecommercially available. When more than a single wavelength ofelectromagnetic radiation is used in the arrangement of FIG. 1, a broadband π-cell may be utilized to provide half-wave retardation of eachwavelength to maintain the same intensity level for each wavelength.

[0041] Logic tree 1 of FIG. 1 is activated from a source 17 ofelectromagnetic radiation which may be a laser or any other source ofradiation the output of which may be converted from a linearly polarizedorientation to a circularly polarized orientation by means of aquarter-wave plate (not shown) in a manner well known to those skilledin the optical arts. If the resulting output is not appropriatelypolarized, a half-wave retarder may be utilized to provide theconversion from one circular polarization to the other polarization.

[0042] For purposes of the present application, radiation emanating fromsource 17 is circularly polarized in either a clockwise orcounter-clockwise direction. Lasers which are commercially available maybe utilized to provide outputs which fall within the visible, infraredor ultraviolet spectra. While source 17 is shown as a single source inFIG. 1, it should be appreciated that it also represents a plurality ofsources each having a different wavelength. Thus, source 17 may includelasers which emit at the red, green and blue wavelengths of the visiblespectrum so that the projected beam of radiation is a beam of lighthaving a single color or combinations of these wavelengths.

[0043] It should also be appreciated that source 17 may comprise lasersor other sources of electromagnetic radiation which are capable of beingintensity modulated. In this way, the source output may be varied inintensity from zero to a maximum intensity including all gradations inbetween.

[0044] In FIG. 1, source of electromagnetic radiation 17 is showndirectly irradiating a member 60 of active element 18 of branch 2 fromwhich it is either transmitted or reflected depending on thepolarization of the emitted radiation. The emitted radiation from source17 may have a single intensity or it may be an intensity modulatedsignal provided by a television camera 25 or the like. By appropriatelyprogramming π-cells or half-wave retarders 61, an unmodulated orintensity modulated signal is delivered in a scanned manner to theactive and passive CLC elements 41-56 of branches 9-16 of STAGE 4. Inthis way, an unmodulated or intensity modulated beam of radiation isscanned across elements 41-56 providing an output which is similar inevery way to a single scan line of a conventional television set.

[0045] If an input is provided in digital form, a digital-to-analogconverter 26 may be interposed between camera 25 and source 17 in awell-known manner.

[0046] In FIG. 1, variable half-wave retarders 61 are activated by aprogrammable pulsed source 27 which gets timing information from camera25 via interconnection 28. A plurality of driver interconnections 29extend from pulsed source 27 and each interconnection 29 is connected toa separate electrode 62 which applies an electric field to an associatedhalf-wave retarder 61 when activated by pulsed source 27. In FIG. 1,fifteen driver interconnections 29 would be utilized each one of which,when pulsed, activates a separate variable half-wave retarder 61.

[0047] In operation, logic tree 1 is activated when source 17 isactivated. The object is to provide a scanned output from a single inputto a plurality of outputs in STAGE 4 of logic tree 1. It is, therefore,required that the outputs of active and passive elements 41, 43, 45, 47,49, 51, 53, 55 and 42, 44, 46, 48, 50, 52, 54 and 56, respectively, beactivated so that outputs are obtained from these elements in the ordershown in FIG. 1. Since element 41 is to provide the first output, if theinput signal is right-hand circularly polarized (RCP) radiation and allmembers 60 are designed to be reflective of left-hand circularlypolarized (LCP) radiation, the RCP light passes through active elements18, 21, 31 and 41 unhindered since these elements reflect LCP radiationand transmit RCP radiation. An RCP radiation output, therefore, appearsat the output port of element 41.

[0048] In the next time period, half-wave retarder 61 of element 41 isactivated by a pulse from pulsed source 27 via an interconnection 29 toelectrode 62 causing retarder 61 to introduce a half-wave delay into theinput RCP radiation which has passed through active elements 18, 21 and31 causing the RCP radiation to be converted to LCP radiation. The LCPradiation then reflects from member 60 of element 41 which is reflectiveof LCP radiation toward member 60 of element 42 which is also reflectiveof LCP radiation. The impinging LCP radiation is then reflected to theoutput port of element 42.

[0049] In the next time period, an output is desired from the outputport of active element 43. To accomplish this, retarders 61 at theinputs of active elements 31 of STAGE 3 and active elements 43 of STAGE4 are activated by applying pulses to their associated transparentelectrodes 62.

[0050] Once this is done, the RCP radiation at the input of activeelement 31 is converted to LCP radiation and reflects from LCPreflective member 60 over to LCP reflective member 60 of passive element32 where it is reflected toward active element 43. The LCP input atactive element 43 encounters a half-wave retarder 61 and is converted toRCP radiation. The latter then passes unaffected to the output port ofactive element 43 because its CLC member 60 reflects only LCP radiation.

[0051] In the next interval, pulsed source 27 deactivates half-waveretarder 61 associated with active element 43 and continues activationof the half-wave retarder 61 associated with active element 31. In thisway, the LCP radiation impinging on element 43 encounters no delay andremains as LCP radiation which is then reflected from LCP reflectivemember 60 of element 43 toward passive element 44. The thus reflectedLCP radiation is reflected from LCP reflective member 60 of element 44to its output port.

[0052] Rather than tediously describing every passage through everyelement, the order of the activation of half-wave retarders 61 will bedescribed since every path from input to output port can be gleaned fromthe previous description and drawing shown in FIG. 1. To obtain anoutput at active element 45, only the variable half-wave retarders 61associated with active elements 21 and 33 must be activated. To obtainan output at active element 46, variable half-wave retarders 61associated with active elements 21, 33 and 45 must be activated. Toobtain an output at active element 47, the variable half-wave retardersassociated with active elements 21 and 47 must be activated. To obtainan output at passive element 48, only the variable half-wave retarderassociated with active element 21 need be activated. An output at activeelement 49 may be obtained by activating the half-wave retardersassociated with active elements 18 and 23. An output at passive element50 may be obtained by activating the half-wave retarders associated withactive elements 18, 23 and 49. To obtain an output at active element 51,the half-wave retarders associated with active elements 18, 35 and 51must be activated. An output may be obtained from passive element 52 byactivating half-wave retarders 61 associated with active elements 18, 23and 35. To obtain an output at active element 53, half-wave retarders 61associated with active elements 18 and 37 must be activated. An outputat passive element 54 may be obtained by activating half-wave retarders61 associated with active elements 18, 37 and 53. To obtain an output atactive element 55, half-wave retarders 61 associated with activeelements 18 and 55 are activated. Finally, active element 56 isactivated by activating half-wave retarder 61 associated with activeelement 18.

[0053] Once half-wave retarders 61 are activated by applying pulses totransparent electrodes 62 from programmable pulsed source 27 asdescribed hereinabove, a scanned output varying in intensity at each ofthe active and passive elements 41 through 56 is obtained. The outputsdo not all have the same polarization and, for the embodiment of FIG. 1,have a polarization pattern of alternating RCP and LCP as the elementsare scanned from left to right. Recognizing that such variation ispresent is important where outputs having the same circular polarizationare desired or required so that fixed half-wave retarders may be placedto convert all the polarization's to the same polarization. Thus, inFIG. 1, for example, fixed half-wave retarders 63 may be placed at theoutputs of active elements 41, 43, 45, 47, 49, 51, 53 and 55 to converttheir RCP outputs to LCP. The ability to do this conversion isparticularly important in arrangements which provide a 3-D outputbecause the perception of 3-D is based on having two spatially displacedimages each of which has a different polarization.

[0054] If the input to active CLC element 18 in FIG. 1 is changed to LCPand all the CLC members 60 in logic tree 1 are changed to be reflectiveof RCP, the outputs obtained are exactly the same as those shown in FIG.1.

[0055] An identical output pattern to that shown in FIG. 1 is obtainablewhere the input is LCP and all the members 60 are reflective of LCP.

[0056] A pattern opposite to that shown in FIG. 1 is obtainable wherethe input is RCP and all the members 60 are reflective of RCP.

[0057]FIG. 2 is a schematic diagram of a logic tree 1 similar to thatshown in FIG. 1. It shows only the logic tree without the associatedlaser and electronics. The purpose is to show that the polarization ofmembers 60 reflective of different polarizations may be varied toproduce outputs having different polarizations from those shown inFIG. 1. Each of the boxes representing active and passive elements inFIG. 2 contains either the letter L or R indicating that the CLC member60 therein is reflective of either left-handed or right-handed circularpolarization. Without going into exhaustive detail, suffice it to saythat the outputs shown in FIG. 2 are obtained from an LCP input havingthe following polarization pattern when retarders 61 are switched in thesame order as described in connection with FIG. 1:

[0058] LRRL RLLR RLLR LRRL

[0059] A pattern different from that shown above would be obtained ifthe input polarization were changed to RCP and members 60 of logic tree1 were reflective of polarization's opposite to those shown in FIG. 2.The output pattern is as follows:

[0060] RLLR LRRL LRRL RLLR

[0061] The foregoing illustrates how the output polarization may becontrolled for applications where information is polarization encoded orscrambled; transmitted and decoded or unscrambled by using a key whichcontrols the variable half-wave retarders 61.

[0062] From the point of view of ease of manufacturing, logic treeshaving the same CLC members 60 are the most advantageous as will be seenwhen the fabrication process is described hereinbelow.

[0063] The arrangement of FIG. 1 provides an advantage over the scanningarrangement shown in U.S. Pat. No. 5,459,591 in that input light has totraverse, in a 1024×1024 array, 1024 CLC members 2 (in the patent) toprovide an output at its furthest imaging cell 1 (in the patent). Ifeach CLC member has transmissibility (T), the final imaging cell willhave a transmissibility of (T)¹⁰²⁴. Thus, even with a transmissibilityapproaching 1, say 0.999, the output at the 1024^(TH) imaging cell wouldbe: (0.999)¹⁰²⁴ which, to all intents and purposes, is zero.

[0064] Opposed to this is the present approach where, to provide thelast output in a 1024×1024 array, only twenty CLC members 60 or two perstage need to be traversed providing a transmissibility of (T)²⁰. Underthese conditions the 1024th output, assuming T=0.999, would be (0.999)²⁰which is approximately ninety percent of the input intensity. Theminimum transmissibility for a ten stage array would be (T)¹⁰ or onetransition per stage.

[0065] From the foregoing, while logic tree 1 of FIG. 1 represents animprovement over the prior art in terms of output light intensity, itshould be clear that each logic tree 1 requires its own input laser orsource of electromagnetic radiation 17. Thus, to provide an 8×8 array,for example, eight logic trees 1 would have to be stacked in the mannershown in FIG. 3.

[0066]FIG. 3 is an orthographic projection of eight logic trees 1positioned one atop the other which, in accordance with the teaching ofthe present application, provide 64 outputs. One source ofelectromagnetic radiation 17 per logic tree 1 is required.

[0067] Because of space limitations, the showing of FIG. 3 has beenlimited to the use of only three of the STAGES of FIG. 1. Also, sinceeach of logic trees 1 in FIG. 3 is identical with the other logic trees1, only the topmost logic tree 1 with its CLC members 60 and variablehalf-wave retarders 61 have been shown. Also, as will become clearhereinafter, the dimensions shown are not to scale.

[0068] In FIG. 3, 8×8 array 70 is shown which comprises eight logictrees 1 stacked one atop the other. Each logic tree 1 is comprised ofthree stages, STAGE 1, STAGE 2, and STAGE 3. STAGE 1 comprises branch 2;STAGE 2 comprises branches 3, 4 and STAGE 3 comprises branches 5-8 asshown in FIG. 1. Each branch includes active and passive CLC elementssimilar to those shown in STAGES 1-3 of FIG. 1 and each of the activeand passive elements includes a cholesteric liquid crystal member 60which is positioned at an angle of 45° within each of the active andpassive elements of array 70. Also, included are variable half-waveretarders 61 which are arranged in FIG. 3 just like the variableretarders 61 in STAGES 1-3 of FIG. 1. In FIG. 3, each logic tree 1 isactivated by an associated source of electromagnetic radiation 17,preferably a laser, thus requiring a total of eight sources 17. As eachlaser is actuated, variable half-wave retarders 61 are actuated asdescribed in connection with FIG. 1 hereinabove and the output of eachlaser 17 appears as a scanned modulated signal going from left to rightat the outputs of imaging cells 71 of each of logic trees 1. In thearrangement shown in FIG. 3, sources 17 and retarders 61 may be actuatedsequentially or simultaneously. If the outputs of sources 17 areconverted to right-hand circular polarization (RCP) and all CLC members60 are reflective of left-hand circular polarization (LCP), the outputsof each logic tree 1 of FIG. 3 will be the same as those shown in FIG.1, namely:

[0069] RLRL RLRL

[0070] As suggested in connection with the description of FIG. 1, fixedhalf-wave retarders may be appropriately positioned to make all theoutputs have the same polarization.

[0071] While the number of lossy transitions per logic tree has beenreduced over that shown in the prior art, this has been accomplished bythe use of a source 17 for each logic tree 1 incorporated in an array70. With arrangements like that shown in FIG. 3 expanded to a 1024×1024array, for example, 1024 sources 17 would be required. This requirementcan be eliminated and the number of sources reduced to one by using alogic tree 1 like that shown in FIG. 1, the outputs of which, providedfrom a single source 17, act as inputs to an array 70 like that shown inFIG. 3.

[0072] This will become clear from a consideration of FIG. 4 which is anorthographic projection similar to FIG. 3 except that, instead of aplurality of sources 17, only a single source 17, in combination with alogic tree 1 like that shown in FIG. 1, disposed perpendicularly to thelogic trees 1 of FIG. 3 is required.

[0073] Considering FIG. 4 in more detail, array 70 is identical witharray 70 shown in FIG. 3. Also, source of electromagnetic radiation 17in FIG. 4 is similar to sources 17 shown in FIB. 3. In FIG. 4, an inputlogic tree 72 is shown disposed between array 70 and source 17 such thateach imaging cell 71 of logic tree 72 acts as an input to an associatedlogic tree 1 of array 70. Thus, the uppermost imaging cell 71 of inputlogic tree 72 provides an input to the leftmost element of the topmostof logic trees 1 of array 70. This input which may be an intensitymodulated signal from source 17, is scanned across the imaging cells 71of the topmost logic tree 1 of array 70 in a manner analogous to thescan of a television frame. When the scanned output of the topmost logictree 1 reaches its last imaging cell 71, the output of source 17 isswitched to the next imaging cell 71 (immediately beneath the topmostimaging cell 71) of logic tree 72. The output of that next imaging cellthen acts as the input to the logic tree 1 immediately beneath thetopmost logic tree 1 of array 70. The inputs to the last mentioned logictree 1 are then delivered to the imaging cells 71 of that logic tree 1in sequence from left-to-right providing a scanned, intensity modulatedsignal similar to that of a television scan line.

[0074] Each of the remaining imaging cells 71 of input logic tree 72 isthen actuated by programming electrodes 62 and variable half-waveretarders 61 associated with logic tree 72 in the same manner describedhereinabove in connection with FIG. 1. Similarly, each of the logictrees 1 of array 70 is actuated by outputs from an associated imagingcell 71 of input logic tree 72. Then, under control of programmedelectrodes 62 and half-wave retarders 61, these outputs, now inputs, toan associated logic tree 1, are delivered to the imaging cells 71 ofeach logic tree 1 as a scanned line having portions which may vary inintensity from imaging cell 71-to-imaging cell 71. In this way, byaccessing logic trees 1 from top-to-bottom, for example, in FIG. 4, animage is built up which, depending on the imaging cell density, canprovide images of extremely high resolution.

[0075] From the foregoing, it should be clear that the modulated outputof a single source 17, preferably a laser, may be delivered to theimaging cells 71 of a plurality of stacked logic trees 1 like array 70in FIG. 4. As shown in FIG. 4, the use of an input logic tree 72 permitsthe use of a single source 17 as opposed to the multiplicity of sources17 shown in FIG. 3. The value of the arrangement shown in FIG. 4 becomesmore apparent when it is recalled that for a 1024×1024 array embodimentlike FIG. 3, 1024 lasers would be required. Thus, in addition toreducing the number of lossy transitions as provided by the embodimentof FIG. 3, the embodiment shown in FIG. 4 also reduces the number ofsources 17 required to the absolute minimum of one. While the electronicequipment required to operate displays like those shown in FIGS. 3, 4,has not been shown, it should be appreciated that the same components asshown in FIG. 1 and which are well-known in the imaging arts may beutilized in the practice of the present invention. Thus, timinginformation obtained from camera 25, for example, is applied viainterconnection 28 to programmable pulsed sources 27. The latter thenapplies switching signals to both logic tree 72 and each of logic trees1 to appropriately control their electrodes 62 and half-wave retarders60 so that a scanned energy output may be delivered from the imagingcells 71 of each logic tree 1 and input logic tree 72.

[0076] Referring now to FIG. 5, an orthographic projection of an imagingarray is shown which, in combination with viewing glasses and stereodisplaced images provides a 3-D display.

[0077] In FIG. 5, input logic tree 72 is accessed by a source 17 ofelectromagnetic radiation which is modulated by outputs of astereoscopic television camera 73 via interconnection 74. The twooutputs from stereo camera 73 are stereo displaced so that, if they areseparated one from the other by some characteristic like polarization,the two resulting images may be delivered one to each eye (usingappropriate glasses) and combined in the brain to provide athree-dimensional image.

[0078] One of the images is provided by applying scanned lines fromstereo camera 73 via interconnection 74 to laser 17. The output of thelatter is then applied to input logic tree 72 from which scanned lineoutputs are delivered from the topmost and alternate imaging cells 71under control of programmable pulsed source 75 which actuates variablehalf-wave retarders 61 thereof via interconnections 76. The output fromthe topmost of imaging cells 71 of input logic tree 72 is applied for agiven interval to leftmost member 60 of the uppermost of logic trees 1.At the same time, variable half-wave retarders 61 under control ofprogrammable pulsed source 27 are appropriately actuated so that aportion of the scanned line from stereo camera 73 is delivered to eachof the imaging cells 71 of the uppermost of logic trees 1 of array 70.

[0079] In the instance of FIG. 5, each imaging cell 71 of array 70 isilluminated for a time equal to ⅛ the given interval of a scanned linefrom camera 73. For a 1024×1024 array, the illuminating time would be{fraction (1/1024)}^(TH) of the scanned line interval.

[0080] The first image is completed by applying scanned lines fromstereo camera 73 via interconnection 74 which modulate laser 17 duringeach alternate interval after the first to each alternate imaging cell71 after the first imaging cell 71 of input logic tree 72. Each scannedline is delivered to the imaging cells 71 of each alternate logic tree 1of array 70 in the same manner described in connection with the deliveryof the first scanned line to the uppermost of logic trees 1 of array 70.

[0081] The stereo displaced image from stereo camera 73 is delivered asscanned lines via interconnection 74 to laser 17 where they modulate theoutput of laser 17. The stereo displaced scanned line outputs aredelivered to laser 17 during the second and alternate intervals afterthe second interval. The first stereo displaced output from laser 17,under control of programmable pulsed source 75 which appropriatelyactuates the variable half-wave retarders 61 of input logic tree 72, isdelivered to the second-from-the-top of imaging cells 71 of logic tree72 as a scanned line. This last mentioned output acting as an input tothe leftmost CLC member 60 of the second-from-the-top of logic trees 1of array 70 is delivered to the imaging cells 71 of thesecond-from-the-top of logic trees 1 of array 70 under control ofprogrammable pulsed source 27 as portions of the scanned line output oflaser 17.

[0082] As with the first image generation, the imaging cells 71 of thestereo displaced image are illuminated for a time equal to ⅛ the giveninterval of a scanned line.

[0083] The stereo displaced image is completed by applying scanned linesfrom stereo camera 73 via interconnection 74 to laser 17 during eachalternate interval after the second interval to each alternate imagingcell 71 after the second imaging cell 71 of input logic tree 72. Eachstereo displaced scanned line is delivered to the imaging cells 71 ofthe second and alternate logic trees 1 of array 70 in the same mannerdescribed in connection with the delivery of the first stereo displacedscanned line to the second-from-the-top of logic trees 1 of array 70.

[0084] If the polarization applied to logic trees 1 is RCP and themembers 60 thereof are designed to reflect LCP, logic trees 1 provide animage at their imaging cells 71 in the same way described in connectionwith FIG. 1 and the resulting outputs will have polarizations like thoseshown in FIG. 1. The polarizations at STAGE 3 for each of logic trees 1are:

[0085] RLRL RLRL

[0086] To obtain this result, however, input logic tree 72 must provideRCP at all its imaging cells 71. This requires an RCP input from laser71, a logic tree with elements which reflect LCP and fixed half-waveretarders 63 (not shown) disposed after imaging cells 71 which provideLCP outputs.

[0087] To obtain a single polarization for all of the outputs of firstand alternate logic trees 1 of array 70, for example, RCP, the LCPoutputs of these logic trees 1 must be converted to RCP. This isaccomplished by interposing fixed half-wave retarders 63 over theimaging cells 71 having LCP outputs.

[0088] Similarly, to obtain a single but opposite polarization for allof the outputs of the second and alternate logic trees 71, for example,LCP, the RCP outputs of these logic trees 1 must be converted to LCP.This is accomplished by interposing fixed-half wave retarders 63 overthe imaging cells 71 having RCP outputs.

[0089] At this point, two stereo-displaced images appear at the outputimaging cells 71 of array 70. One image has an RCP polarization whilethe other has an LCP polarization. Then, using glasses which have onelens which passes RCP and another lens which passes LCP, a 3-D image isperceived by a viewer.

[0090] In connection with the 3-D embodiment of FIG. 5, it should beappreciated that outputs from stereo camera 73 may be in either digitalor analog form. If the former, the digital signals may be converted toanalog signals using a digital-to-analog converter in a well-known way.Also, to the extent that logic trees 1 are provided with signalsrepresenting a scanned line of an image and a stereo displaced image,these signals are arranged to alternately access alternate ones of logictrees 1 in succession until two stereo displaced images are formed atthe imaging cells 71 of array 70. The scanned lines of an image and astereo displaced image are electronically interlaced so that source 17is modulated first by signals representing a scanned image and then bysignals representing a scanned stereo displaced image and so on insuccession until the two images are formed.

[0091] From FIG. 5, it can be seen that, for a 3-D array, two 4×8interleaved arrays are required, one for an image and another for astereo displaced image. Extrapolating this information to a practicallevel, if 1024 imaging cells are wanted for each image, an array of2048×1024 imaging cells would be required. Using the same approach asdemonstrated by FIG. 5, two 512×1024 interleaved arrays may be used withthe sacrifice of some resolution. In FIG. 5, logic trees 1 have beeninterleaved horizontally for ease of fabrication but, they may beinterleaved vertically without departing from the spirit of the presentapplication.

[0092] Referring now to FIG. 6, there is shown an orthographic, cut-awayprojection of a plurality of layers 80 of insulating material, likeSiO₂, polycarbonate, acrylic or any other appropriate opticallytransparent material, and a plurality of layers 81 of cholesteric liquidcrystal (CLC) material interleaved with layers 80.

[0093] In FIG. 6, layers 80, 81 are subjected to a slicing operationwhich cuts into layers 80, 81 at an angle, preferably 45°. Layers 80, 81may be cut by saws, lasers, jets or other appropriate tool to providelayers 82 which contain CLC members 60 disposed at an angle of 45° ininsulating material as shown in FIG. 7.

[0094]FIG. 7 is a cross-sectional view of a layer of insulating materialin which CLC members 60 are disposed at an angle of 45°. The spacing ofCLC members 60 is determined by controlling the thicknesses ofinsulating layers 80 prior to the slicing step of FIG. 6. Sincealignment of CLC members 60 is important in transmitting electromagneticenergy from stage-to-stage the spacing of members 60 must be carefullycontrolled. Thus, in FIG. 7, the spacing between CLC members 60 is tunits and could comprise STAGE 1, for example, of array 70 of FIG. 4.

[0095]FIG. 8 is a cross-sectional view of a layer of insulating materialin which members 60 are disposed at an angle of 45° and is similar toFIG. 7 except that members 60 are spaced apart by t/2 units. Layer 82and other like layers are fabricated by slicing an arrangement like thatshown in FIG. 6 except that the thicknesses of layers 80 of insulatingmaterial are reduced to half that shown in FIG. 6. After slicing a stacklike that shown in FIG. 6, the resulting layer 82 with a spacing of t/2between members 60 could comprise stage 2, for example, of array 70 ofFIG. 4.

[0096]FIG. 9 is a cross-sectional view of a layer of insulating materialin which members 60 are disposed at an angle of 45° and is similar toFIG. 7 except that members 60 are spaced apart by t/4 units. Layer 82 inFIG. 9 is fabricated by slicing an arrangement like that shown in FIG. 6except that the thicknesses layers 80 would be reduced to one-quarterthat shown in FIG. 6. After slicing a stack like that shown in FIG. 6,the resulting layer 82 with a spacing of t/4 between members 60 couldcomprise STAGE 3, for example, of array 70 of FIG. 4.

[0097] The spacing of members 60 is always reduced by half as additionalstages are added so that higher and higher resolutions may be obtained.Thus, for an array with ten stages, the spacing between CLC members 60would be t/512 units.

[0098] By slicing arrangements like that shown in FIG. 6 and controllingthe thicknesses of layers 80, layers 82 with members 60 spaced apart bydifferent amounts like those shown in FIGS. 7-9 may be easily obtained.As will be seen below, layers 82 with appropriately spaced members 60may be stacked to produce an array 70 like that shown in FIG. 4 or anarray having as many stages as desired. This can be done on amass-production basis to produce literally thousands of layers likelayers 82 of FIGS. 7-9.

[0099]FIG. 10 is a cross-sectional, orthographic projection of a layer82 which contains CLC members 60 disposed at an angle of 45° therein.Layer 82 in FIG. 10 is similar to layer 82 of FIG. 8 except that in FIG.10, a ground plane 83 is deposited or formed on the bottom of layer 82.Layer 83 is transparent and metallic in character and acts as a groundplane for subsequently deposited electrodes which activate variablehalf-wave retarders 61. A material like indium-tin oxide (ITO) may bedeposited or formed in a well-known way on the bottom of layer 82 ofFIG. 10. The transparency of ITO, of course, permits the transmission oflight energy from stage-to-stage with little or no loss in intensity.

[0100] Referring to FIG. 11, there is shown a cross-sectional,orthographic projection similar to FIG. 10 except that electrodes 84 areshown disposed over every other CLC member 60, like they would be iflayer 83 of FIG. 11 were to be utilized as a STAGE 2 in an array 70 likethat shown in FIG. 4. This pattern of electrode spacing will always bethe same regardless of which stage is being considered. Areconsideration of FIG. 1 shows this to be true since each stage alwayscomprises at least one branch consisting of active and passive CLCelements. Electrode 84 (62 in FIG. 1) is always associated with andforms a part of variable half-wave retarders 61 which, in turn, isalways associated with the active CLC element of any branch. Like groundplane 83, electrode 84 is comprised of indium-tin-oxide (ITO) materialwhich is transparent to the electromagnetic radiation being utilized. Toobtain electrodes 84 in the form shown in FIG. 11, indium-tin oxide isformed atop layer 82 and, using well-known lithographic, masking andetching techniques, electrodes 84 are appropriately positioned overevery other CLC member 60. Rather than carrying out two separatedeposition steps for ground plane 83 and electrodes 84, the ITO materialmay be formed simultaneously on each side of layer 82. Then, thephotolithographic, masking and etching steps are carried out.

[0101] Referring now to FIG. 12, there is shown a cross-sectional viewof a layer 82 similar to that shown in FIG. 11 except that a spacer isadded around the periphery of layer 82 and the thus enclosed volume isfilled with a phase-shifter material in liquid form.

[0102] In FIG. 12, a spacer 85 is formed around the periphery of layer82 by, for example, gluing a spacer 85 of insulating material around theedge of layer 82. Spacer 85 separates layers 82 from other overlyinglayers and defines the volume into which phase-shifter material 86 isplaced.

[0103]FIG. 13 is a top view of a logic tree 1 made up of layers 82 likethose shown in FIGS. 7-12. The arrangement of FIG. 13 shows the topmostlogic tree 1 of FIG. 4 after it has been fabricated in accordance withthe teaching of the present application. FIG. 13 can also be considereda side-view of input logic tree 72 since its structure does not departin any way from the structure of logic tree 1.

[0104] One way of assembling the structure of FIG. 13, is to stack afinished layer 82 like that shown in FIG. 12 on a finished layer 82 likethat shown at the bottom of FIG. 13. Another layer 82 like that shown atthe top of FIG. 13 is stacked atop the finished layer 82 of FIG. 12. Thelayers are glued together with the topmost layer 82 forming STAGE 1 asshown in FIG. 4; the middle layer 82 forming STAGE 2 as shown in FIG. 4and the bottom layer 82 forming STAGE 3 as shown in FIG. 4. Thus, inputsprovided to the leftmost CLC member 60 of topmost layer 82 will, undercontrol of inputs to electrodes 84 from pulsed source 27, appear asoutputs emanating, from left-to-right, from CLC members 60 of bottommostlayer 82 as a scanned line of modulated or unmodulated light.

[0105] For the array, once stacked, the top and bottom thereof may becovered with insulating layers, one of which contains holes whichregister with the ends of electrodes 84 and ground planes 83. Thus, evenwhen logic trees 1 are not being utilized, their associated electrodes61, 84 which extend from top-to-bottom of array 70 and are electricallyconnected as shown in FIG. 5 are simultaneously energized.

[0106] Inputs to the stacked logic trees 1 are provided, as shown inFIG. 4, from imaging cells 71 of input logic tree 72. The orientation ofinput logic tree 72 with respect to array 70 is best shown in FIG. 4which does not depart in any way from the arrangement of FIG. 13. Thelatter figure merely shows the structural details to better effect.Thus, as previously explained in FIG. 4, outputs from imaging cells 71of input logic tree 72 are scanned from top-to-bottom of tree 72 andeach output initially accesses the leftmost member 60 of its associatedlogic tree 1 such that outputs appear at imaging cells 71 of array 70 asa plurality of left-to-right scans which go from the topmost logic tree1 to the bottommost logic tree 1 of array 70.

[0107] Input logic tree 72 may take the form of an array 70 rotated 90°so that imaging cells 71 there of register with the leftmost retarder 61of each of the logic trees 1 like lasers 17 as shown in FIG. 3. In thisinstance, only a single logic tree 1 of the rotated array 70 isenergized.

[0108] Alternatively, the array shown in FIG. 13 may be fabricatedwithout introducing the phase shifter material 86. The structure of FIG.13 is then sliced in a direction parallel to the surface there ofresulting in a structure similar to input logic tree 72 as shown in FIG.4. The resulting slice is placed on an insulating layer and bonded toit. A cover layer of insulating material having holes therein whichregister with electrodes 84 and ground planes 83 is fabricated bydrilling or etching using well-known photolithographic techniques. Thevolumes enclosed by the insulation layer are now filled with liquidphase shifter material 86. The cover layer is affixed to the other sideof the logic tree slice. A metallic layer such as aluminum is thendeposited on the surface of the cover layer and in the holes previouslyformed therein. Then, using well-known photolithographic masking andetching techniques, conductors to electrodes 84 in a ground planes 83are formed

[0109] Without going into exhaustive detail, it should be appreciatedthat the side of input logic tree 72 of FIG. 4 may be butted against theback of array 70. In this way, the overall thickness of the arrangementof FIG. 4 is substantially reduced. Well-known optical techniques usingreflectors may be used to apply a 90° turn to light emanating fromimaging cells 71 of tree 72 when it is butted against the back of array70.

[0110] Since electrodes 84 extend from front-to-back on each logic tree1 as shown, for example, in FIG. 13, they are best accessed from thefront or back of the array with activating metallic lines 29, as shownin FIG. 4, extending in insulated spaced relationship with a surface ofarray 70 to a plug which can be connected to pulsed source 27, forexample. This may be accomplished using well-known photolithographic andetching techniques.

[0111] The arrangements shown in FIGS. 6-12 may have the followingtypical dimensions: Layers 82 0.5 mm thick and up Electrodes 84 500 Å to1000 Å thick Ground Planes 83 500 Å to 1000 Å thick Spacer 85 1μ to 10μthick Elements 60 2μ to 30μ thick Cells 71 0.5 mm wide and up. Mayexceed 10 cm

[0112] Typical voltages applied to electrodes 84 may range between 5Vand 100V.

[0113] From the foregoing, it should be clear that arrays 70 may rangein size from that typical of T.V. sets used in the home to displayssimilar to those used in stadia. The resulting arrays are flat, lightweight, require but a single laser source or multiple laser sources andare inexpensive and easily fabricated.

1. A logic tree branch for steering electromagnetic energy comprisinganactive element for directing said electromagnetic energy into one offirst and second paths and a passive element disposed in said secondpath for directing said electromagnetic energy into a path parallel tosaid first path when said electromagnetic energy is directed into saidsecond path.
 2. A logic tree branch according to claim 1 furtherincluding a source of said electromagnetic energy having a givenwavelength and circular polarization coupled to said active element. 3.A logic tree branch according to claim 2 wherein said active elementincludes an element transmissive to said given polarization andwavelength and reflective to said given wavelength and a polarizationopposite to said given polarization.
 4. A logic tree branch according toclaim 2 wherein said passive element includes an element reflective tosaid given wavelength and a polarization opposite to said givenpolarization.
 5. A logic tree branch according to claim 2 wherein saidactive element includes phase shifter means disposed between said sourceof electromagnetic energy and said active element.
 6. A logic treebranch according to claim 2 wherein said active element includes anelement made of cholesteric liquid crystal material.
 7. A logic treebranch according to claim 2 wherein said passive element includes anelement made of cholesteric liquid crystal material.
 8. A logic treebranch according to claim 2 further including a programmable pulse ofsource connected to said active element.
 9. A logic tree branchaccording to claim 2 further including means connected to said source ofelectromagnetic energy for modulating said source.
 10. A logic treebranch according to claim 5 wherein said phase shifter means includes aphase shifting material responsive to different potential levels forswitching said phase shifting material between states which provideelectromagnetic energy having said given polarization and said oppositepolarization.
 11. A logic tree branch according to claim 5 wherein saidphase shifting means further includes electrode means for applying saiddifferent potential levels to said phase shifter material.
 12. A logictree for steering electromagnetic energy comprising a plurality ofstages, the first of said stages including a branch for directing saidenergy to a similar branch in each succeeding stage, each of said stagescontaining 2^(n−1) branches where n is the stage number.
 13. A logictree according to claim 12 wherein each of said branches includes anactive element for directing said electromagnetic energy into one offirst and second paths and a passive element disposed in said secondpath for directing said electromagnetic energy into a path parallel tosaid first path when said energy is directed into said second path. 14.A logic tree according to claim 13 further including a source of saidelectromagnetic energy having a given wavelength and circularpolarization coupled to said active element of said first stage.
 15. Alogic tree according to claim 14 wherein said active element includes anelement transmissive to said given wavelength and circular polarizationand reflective to said given wavelength and to a circular polarizationopposite to said given circular polarization.
 16. A logic tree accordingto claim 14 wherein said passive element includes an element reflectiveto said given wavelength and a circular polarization opposite to saidgiven circular polarization.
 17. A logic tree according to claim 14wherein said active element includes phase shifter means disposed inelectromagnetically coupled relationship with said active element.
 18. Alogic tree according to claim 14 wherein said active element includes anelement made of cholesteric liquid crystal material.
 19. A logic treeaccording to claim 14 wherein said passive element includes an elementmade of cholesteric liquid crystal material.
 20. A logic tree accordingto claim 14 further including a programmable pulsed source connected tosaid active element.
 21. A logic tree according to claim 14 furtherincluding means connected to said source of electromagnetic energy formodulating said source.
 22. A logic tree according to claim 14 furtherincluding half-wave retarders disposed in electromagnetically coupledrelationship with selected of said active and passive elements of thelast stage of said plurality of stages to convert said electromagneticenergy emanating from said active and passive elements to a singlecircular polarization.
 23. A logic tree according to claim 17 whereinsaid phase shifter means includes a phase shifting material responsiveto different potential levels for switching said phase shifting materialbetween states which switch incident electromagnetic energy between saidgiven polarization and said opposite polarization.
 24. A logic treeaccording to claim 23 wherein said phase shifting means further includesmeans for applying said different potential levels to said phase shiftermaterial.
 25. A flat panel logic tree display array for steeringelectromagnetic radiation comprising a plurality of first logic treeseach of said first logic trees having a plurality of stages, a singleinput port, a plurality of output ports, and wherein said array has 2m×2^(n) output ports and m and n are stage numbers.
 26. An arrayaccording to claim 25 further including a plurality of sources ofelectromagnetic radiation each electromagnetically coupled to said asingle input port of an associated first logic tree and having a givenwavelength and circular polarization.
 27. An array according to claim 25further including a second logic tree similar to each of said pluralityof first logic trees having a plurality of stages, a single input portand a plurality of output ports each of said output ports of said secondlogic tree being connected to a different one of said input ports ofsaid plurality of first logic trees.
 28. An array according to claim 26wherein the first stage of said plurality of stages includes a branchfor directing said radiation to a similar branch in each succeedingstage, each of said stages containing 2^(n−1) branches where n is thestage number. 29 An array according to claim 27 further including atleast a single source of electromagnetic radiation electromagneticallycoupled to said single port of said second logic tree.
 30. An arrayaccording to claim 27 further including a half-wave retarderelectromagnetically coupled to selected ones of said output ports ofsaid plurality of first logic trees.
 31. An array according to claim 27further including a half-wave retarder electromagnetically coupled toselected ones of said output ports of said plurality of first logictrees.
 32. An array according to claim 27 wherein said plurality ofoutput ports of said plurality of first logic trees are disposed in theform of a rectilinear array.
 33. An array according to claim 27 whereinsaid plurality of first logic trees and said second logic tree aredisposed in a orthogonal relationship.
 34. An array according to claim27 wherein each of said plurality of first logic trees is disposed instacked relationship with others of said first logic trees.
 35. An arrayaccording to claim 27 wherein said plurality of output ports of saidsecond logic tree are remote from each said single input port of saidplurality of first logic trees.
 36. An array according to claim 27further including at least a single source of electromagnetic radiationoptically coupled to said single input port of said second logic treeand means connected to said at least a single source for modulating saidat least a single source of electromagnetic radiation.
 37. An arrayaccording to claim 27 wherein the first stages of said plurality ofstages of said first logic trees and the first stage of said secondlogic tree include a branch for directing said radiation to a similarbranch in each succeeding stage, each of said stages containing 2^(n−1)branches where n is the stage number.
 38. An array according to claim 28wherein each of said branches includes an active element for directingsaid electromagnetic radiation into-one of first and second paths and apassive element disposed in said second path for directing saidradiation into a path parallel to said first path when said radiation isdirected into said second path.
 39. An array according to claim 28wherein said active element includes an element transmissive to saidgiven wavelength and circular polarization and reflective to said givenwavelength and to a circular polarization opposite to said givencircular polarization.
 40. An array according to claim 28 wherein saidpassive element includes an element reflective to said given wavelengthand a circular polarization opposite to said given circularpolarization.
 41. An array according to claim 28 wherein said activeelement includes phase shifter means disposed in electromagneticallycoupled relationship with said active element.
 42. An array according toclaim 28 wherein said active element includes an element made ofcholesteric liquid crystal material.
 43. An array according to claim 28wherein said passive element includes an element made of cholestericliquid crystal material.
 44. An array according to claim 28 furtherincluding a programmable pulsed source connected to said active element.45. An array according to claim 28 further including means connected tosaid source of electromagnetic radiation for modulating said source. 46.An array according to claim 28 further including half wave retardersdisposed in electromagnetically coupled relationship with selected ofsaid active and passive elements of the last stage of said plurality ofstages to convert said electromagnetic energy emanating from said activeand passive elements to a single circular polarization.
 47. An arrayaccording to claim 37 wherein each of said branches of said first andsecond logic trees includes an active element for directing saidelectromagnetic radiation into one of first and second paths and apassive element disposed in said second path for directing saidradiation into a path parallel to said first path when said radiation isdirected into a first path.
 48. An array according to claim 37 whereinsaid active element includes an element transmissive to said wavelengthand circular polarization and reflective to said given wavelength and toa circular polarization opposite to said given circular polarization.49. An array according to claim 37 wherein said passive element includesan element reflective to said given wavelength and a circularpolarization opposite to said given circular polarization.
 50. An arrayaccording to claim 37 wherein said active element includes phase shiftermeans disposed in electromagnetically coupled relationship with saidactive element.
 51. An array according to claim 37 wherein said activeelement includes an element made of cholesteric liquid crystal material.52. An array according to claim 37 wherein said passive element includesan element made of cholesteric liquid crystal material.
 53. An arrayaccording to claim 37 further including a programmable pulsed sourceconnected to said active element.
 54. An array according to claim 37further including means connected to said source of electromagneticenergy for modulating said source.
 55. An array according to claim 37further including half-wave retarders disposed in electromagneticallycoupled relationship with selected of said active and passive elementsto convert said electromagnetic energy of the last stage of saidplurality of stages to convert said electromagnetic energy emanatingfrom said active and passive elements to a single circular polarization.56. An array according to claim 41 wherein said phase shifter meansincludes a phase shifting material responsive to different potentiallevels for switching said phase shifting material between states whichswitch incident electromagnetic radiation between said givenpolarization and said opposite polarization. 57 An array according toclaim 50 wherein said phase shifter means includes a phase shiftingmaterial responsive to different potential levels for switching saidphase shifting material between states which switch incidentelectromagnetic energy between said given polarization and said oppositepolarization.
 58. An array according to claim 56 wherein said phaseshifting means further includes means for applying said differentpotential levels to said phase shifter material.
 59. An array accordingto claim 57 wherein said phase shifting means further includes means forapplying said different potential levels to said phase shifter material.60. A method for fabricating an array comprising the steps of: forming aplurality of insulating media having a plurality of wavelength andpolarizing elements embedded therein at an angle relative to thesurfaces of said media such that the spacing between elements halves foreach different medium in said plurality of said media, forming a phaseshifter arrangement such that a portions thereof of conductive materialare disposed on one of said surfaces of said media in registry withevery other element in each of said media and other portions of which ofconductive material are disposed on another of said surfaces overlappingall of said elements, and, a phase shifting material disposed over atleast said every other element stacking said plurality of media suchthat the topmost insulating medium has two elements and each succeedingmedium has twice as many elements as a preceding medium.
 61. A methodaccording to claim 60 wherein the steps of forming a plurality ofinsulating media includes the steps of: stacking alternating layers ofan insulating material and a wavelength and polarization sensitivematerial the thickness of said layers of insulating material determiningthe spacing between said elements, and slicing said layers at an angleto form said plurality of insulating media with said elements embeddedtherein.
 62. A method according to claim 60 wherein the steps of forminga phase shifter arrangement include the steps of: depositingtransparent, conductive layers on said surfaces of said insulatingmedia, forming said portions of said conductive material on said one ofsaid surfaces of each of said media by photolithography, affixing aspacer of insulating material about the periphery of said one of saidsurfaces of each of said media, and introducing a phase shiftingmaterial over said one of said surfaces of each of said media.
 63. Amethod according to claim 60 further including the step of sealing thetopmost of said media with a layer of insulating material.
 64. A methodaccording to claim 60 wherein said insulating media are made of SiO₂.65. A method according to claim 60 wherein said insulating media aremade of optically transparent layers.
 66. A method according to claim 60wherein said elements are made of cholesteric liquid crystal material.67. A method according to claim 60 wherein said angle is 45°.
 68. Amethod according to claim 60 wherein said conductive material is indiumtin oxide.
 69. A method according to claim 62 wherein said phaseshifting material is in liquid form.
 70. A method according to claim 62wherein said phase shifting material is a liquid crystal.
 71. A methodaccording to claim 62 wherein said phase shifting material is a solidstate electro-optic material.